Various systems of counting have been developed in the prior art for the purpose of, for example, counting the number of newspapers conveyed from a newspaper press. These systems fall generally into mechanical, ultrasonic, laser, and infrared categories.
For years, mechanical counters have been used to count newspapers in overlapped stream conveyors and to control the cycling of newspaper stackers. In a few isolated cases, the counts obtained have been fed to totalizing devices of several varieties. The principal advantage of mechanical counters is their relatively low cost. Disadvantages of such counters include inaccurate counting (especially of small size products and of very large awkward products, such as an inserted package), high maintenance and rapid wear-out. Mechanical counters are poorly suited to use with gripper type conveyors now prevalent in newer installations. Also, mechanical counters will not sense doubles.
Ultrasonic counters pick up perturbations in pressure as papers pass under an electro-mechanical transducer. These devices contain many mechanical components that are subject to fouling by paper dust that pervades the operating environment. Ultrasonic counters are somewhat sensitive to variations in paper-to-transducer distance. Unfortunately, such variations are common in newspaper streams. Like their mechanical counterparts, ultrasonic devices will not sense doubles.
Despite the favorable reputation of many laser devices, their use for newspaper counting gets mixed reviews from users--probably because of their limited shelf life and operating life. The user is not comfortable with the knowledge that a new spare may not work when he needs it. Although the He-Ne lasers commonly used in newspaper counting applications are relatively cheap compared to more powerful laser devices, they do, nonetheless, represent a continuing replacement cost of consequence to the publisher. Laser counters rely on changes in reflected light beams to record counts.
Infrared counters, like laser devices, utilize reflected energy for counting. They are expensive and do not sense thin products as well as thick ones.
In the newspaper publishing business, the need for an accurate count of newspapers being output in a particular press run is essential to the attainment of necessary good business practices. With the ever-increasing and skyrocketing cost of newsprint, it is no longer an acceptable business practice in the publishing field to print more newspapers during a particular press run than the calculated demand. Conversely, it is obviously impractical and poor business practice, and, in fact an unacceptable business practice for a pressroom to print considerably more papers than can be sold. In short, it has become imperative that an extremely accurate print count be obtained on the actual output count of a press run, neither too many nor too few.
All of the prior art sensing means cited above rely upon some sort of perturbation. In the case of mechanical counters, the change is to the unperturbed state of the contact star wheel or other mechanism. In the case of all of the other devices, sensing is accomplished by detecting a change in the emitted energy--such change being the consequence of passage of a newspaper.